Advanced platform for processing crystalline silicon solar cells

ABSTRACT

The present invention generally provides a batch substrate processing system for in-situ processing of a film stack used to form regions of a solar cell device. The batch processing system is configured to process an array of substrates positioned on a substrate carrier. The batch processing system includes a substrate transport interface that provides loading an unloading of the array of substrates in a production line environment. The substrate transport interface may include one or more of a substrate carrier cleaning module, a substrate carrier cooling module, and a substrate carrier buffer module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.12/575,088 [Attny. Docket No. APPM/13855] filed on Oct. 7, 2009, whichis herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to an apparatus and methodfor forming a solar cell device. The invention is particularly usefulfor fabrication of crystalline silicon solar cells processed in batchesarranged in planar arrays.

2. Description of the Related Art

Photovoltaic (PV) or solar cells are devices which convert sunlight intodirect current (DC) electrical power. A typical PV cell includes ap-type silicon wafer, or substrate, typically less than about 0.3 mmthick, with a thin layer of an n-type silicon material disposed on topof the p-type substrate. The generated voltage, or photo-voltage, andgenerated current by the PV cell are dependent on the materialproperties of the p-n junction, the interfacial properties betweendeposited layers, and the surface area of the device. When exposed tosunlight (consisting of energy from photons), the p-n junction of the PVcell generates pairs of free electrons and holes. An electric fieldformed across a depletion region of the p-n junction separates the freeelectrons and holes, creating a voltage. A circuit from n-side to p-sideallows the flow of electrons when the PV cell is connected to anelectrical load. Electrical power is the product of the voltage timesthe current generated as the electrons and holes move through theexternal electrical load and eventually recombine. Each solar cellgenerates a specific amount of electrical power. A plurality of solarcells is tiled into modules sized to deliver the desired amount ofsystem power.

The PV market has experienced growth with annual growth rates exceedingabove30% for the last ten years. Some articles have suggested that solarcell power production world wide may exceed 10 GWp in the near future.It has been estimated that more than 90% of all photovoltaic modules aresilicon wafer based. The high market growth rate in combination with theneed to substantially reduce solar electricity costs has resulted in anumber of serious challenges for silicon wafer production developmentfor photovoltaics.

In order to meet these challenges, the following solar cell processingrequirements generally need to be met: 1) the cost of ownership (CoO)for substrate fabrication equipment needs to be improved (e.g., highsystem throughput, high machine up-time, inexpensive machines,inexpensive consumable costs), 2) the area processed per process cycleneeds to be increased (e.g., reduce processing per Wp) and 3) thequality of the formed layers and film stack formation processes needs tobe well controlled and be sufficient to produce highly efficient solarcells. Therefore, there is a need to cost effectively form andmanufacture silicon sheets for solar cell applications.

Further, as the demand for solar cell devices continues to grow, thereis a trend to reduce cost by increasing the substrate throughput andimproving the quality of the deposition processes performed on thesubstrate. However, the cost associated with producing and supportingall of the processing components in a solar cell production linecontinues to escalate dramatically. To reduce this cost while alsoreducing surface contamination, it is desirable to design a novel solarcell processing system configuration and processing sequence toeliminate and/or combine processing steps and to accommodate sequentialprocessing steps in the processing system that has a high throughput,improved device yield, and a compact footprint.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a processing systemcomprises one or more process chambers each having a substratesupporting surface configured to receive and process an array ofsubstrates positioned on a substrate carrier, a load lock chambercoupled to the one or more process chambers and having one or moreregions with a substrate supporting surface configured to receive andsupport the array of substrates positioned on the substrate carrier, anda substrate carrier interface module positioned adjacent the load lockchamber. In one embodiment, the substrate carrier interface modulecomprises one or more substrate transfer modules configured to loadsubstrates onto the substrate carrier and unload substrates off of thesubstrate carrier and a substrate interface module having a transferrobot configured to transfer the array of substrates on the substratecarrier from the one or more substrate transfer modules to the one ormore regions of the load lock chamber and from the one or more regionsof the load lock chamber to the one or more substrate transfer modules.In one embodiment, the one or more substrate transfer modules include atleast one of a substrate carrier cooling module, a substrate carriercleaning module, and a substrate carrier buffer module.

In another embodiment of the present invention, a substrate carrierloading and unloading system comprises a first substrate transfer moduleconfigured to load an array of substrates onto a substrate carrier, asecond substrate transfer module configured to unload the array ofsubstrates from the substrate carrier, and a substrate interface modulehaving a substrate carrier transfer robot configured to transfer thearray of substrates on the substrate carrier from the first substratetransfer module into a processing system and out of the processingsystem to the second substrate transfer module. In one embodiment, thesubstrate carrier transfer robot is further configured to transfer thesubstrate carrier from the second substrate transfer module to the firstsubstrate transfer module. In one embodiment, the first substratetransfer module comprises a substrate carrier cleaning module, a firstsubstrate carrier lift module, a substrate carrier loading conveyor, andone or more first substrate transfer robots. In one embodiment, thesecond substrate transfer module comprises a substrate carrier coolingmodule, a second substrate carrier lift module, a substrate carrierunloading conveyor, and one or more second substrate transfer robots.

In yet another embodiment of the present invention, a method of forminga solar cell device comprises cleaning a substrate carrier in a carriercleaning module, transferring the substrate carrier from the carriercleaning module to a substrate loading position in a first substratetransfer module, positioning an array of substrates on the substratecarrier in the first substrate transfer module, transferring thesubstrate carrier from the first substrate transfer module to a loadlock chamber using a substrate carrier transfer robot, transferring thesubstrate carrier from the load lock chamber to one or more processchambers and processing the array of substrates on the substratecarrier, transferring the substrate carrier from the one or more processchambers to the load lock chamber, transferring the substrate carrierfrom the load lock chamber to a carrier cooling module using thesubstrate carrier transfer robot and cooling the substrate carrier inthe carrier cooling module, transferring the substrate carrier from thecarrier cooling module to a substrate unloading position in a secondsubstrate transfer module, and removing the array of substrates from thesubstrate carrier in the second substrate transfer module.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is schematic plan view of one embodiment of a substrateprocessing system according to one embodiment described herein.

FIG. 2 is a schematic plan view of a substrate carrier according to oneembodiment described herein.

FIG. 3 is a schematic plan view of a substrate processing systemaccording to one embodiment described herein.

FIG. 4A is a schematic front view of a substrate transport interfaceaccording to one embodiment of the present invention.

FIG. 4B is a schematic front view of a substrate transport interfaceaccording to another embodiment of the present invention.

FIG. 4C is a schematic front view of a substrate transport interfaceaccording to yet another embodiment of the present invention.

FIG. 5 is a schematic, cross-sectional view of a cleaning moduleaccording to one embodiment of the present invention.

FIG. 6 is a schematic, cross-sectional view of a cooling moduleaccording to one embodiment of the present invention.

FIG. 7 is a schematic, cross-sectional view of the buffer moduleaccording to one embodiment of the present invention.

FIG. 8 is a schematic cross-sectional view of a load lock chamberaccording to one embodiment described herein.

FIG. 9 is a schematic cross-section view of a processing chamberaccording to one embodiment described herein.

For clarity, identical reference numerals have been used, whereapplicable, to designate identical elements that are common betweenfigures. It is contemplated that features of one embodiment may beincorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

The present invention generally provides a batch substrate processingsystem, or cluster tool, for in-situ processing of a film stack used toform regions of a solar cell device. In one configuration, a film stackformed on each of the substrates in the batch contains one or morepassivating or dielectric layers and one or more metal layers that aredeposited and further processed within various processing chamberscontained in the processing system. The processing chambers may be, forexample, physical vapor deposition (PVD) or sputtering chambers, plasmaenhanced chemical vapor deposition (PECVD) chambers, low pressurechemical vapor deposition (LPCVD) chambers, hot wire chemical vapordeposition (HWCVD) chambers, ion implant/doping chambers, plasmanitridation chambers, atomic layer deposition (ALD) chambers, plasma orvapor chemical etching chambers, laser anneal chambers, rapid thermaloxidation (RTO) chambers, rapid thermal nitridation (RTN) chambers,rapid thermal annealing (RTA) chambers, substrate reorientation chambers(e.g., flipping chambers), vapor etching chambers, forming gas orhydrogen annealers, plasma cleaning chambers, and/or other similarprocessing chambers.

The substrate processing system may include one or more depositionchambers in which a batch of substrates is exposed to one or moregas-phase materials or RF plasma. In one embodiment, the processingsystem includes at least one plasma enhanced chemical vapor deposition(PECVD) process chamber that has been adapted to simultaneously processa plurality of substrates. In one embodiment, a batch of solar cellsubstrates is simultaneously transferred in a vacuum or inertenvironment to prevent substrate contamination and improve substratethroughput. In the various embodiments of the present invention, eachbatch of substrates is arranged in a planar array for processing asopposed to processing vertical stacks of substrates (e.g., batches ofsubstrates stacked in cassettes). Such processing of batches ofsubstrates arranged in planar arrays allows each of the substrates inthe batch to be directly and uniformly exposed to the generated plasma,radiant heat, and/or processing gases so that each substrate in theplanar array is similarly processed in the processing region of aprocessing chamber. Thus, processing batches of substrates in planararrays does not rely on diffusion type processes or the serial transferof energy to all substrates, such as in conventionally configuredvertical stack or back-to-back batch processing.

In one embodiment, the present invention provides for processing aplanar array of substrates on a substrate carrier. The substrate carriermay be loaded and unloaded in an automated manner in a production lineenvironment. In one embodiment, the invention provides a cleaning modulefor cleaning the substrate carrier prior to loading the array ofsubstrates onto the substrate carrier in order to ensure that any debrispresent on the substrate carrier from previous processing does notinhibit precise and accurate positioning of the array of substrates orintroduce contaminants in subsequent processing of the array ofsubstrates. In one embodiment, the invention provides for cooling thesubstrate carrier having an array of processed substrates disposedthereon in order to inhibit excessive native oxide formation onsubstrates subsequently loaded onto the substrate carrier. In oneembodiment, the present invention provides a buffer module for receivingand storing empty substrate carriers in order to optimize process systemutilization during line stoppages.

FIGS. 1 and 3 illustrate various embodiments of the substrate processingsystem 100 for performing one or more solar cell fabrication processeson a planar array, or batch, of substrates according to the presentinvention. One suitable processing system that may be adapted to performone or more of the processes discussed herein may include a processingplatform, such as a Gen. 5, Gen. 6, or Gen. 8 processing platform,available from Applied Materials, Inc., located in Santa Clara, Calif.

In one embodiment, the substrate processing system 100 typicallyincludes a transfer chamber 110 that is coupled to a substrate transportinterface 150 via a load lock chamber 102. In certain embodiments, thesubstrate processing system 100 has a single transfer chamber 110connected to multiple processing chambers and one or more substratetransport interfaces. In other embodiments, the substrate processingsystem 100 has a multiple transfer chamber configuration to connectmultiple processing chambers and substrate transport interfaces. Eachtransfer chamber 110 generally contains a substrate carrier transferrobot 111 that is adapted to transfer substrates among a plurality ofprocessing chambers (e.g., reference numerals 103-108) and load lockchambers (e.g., reference numerals 102). Examples of robots that may beadapted for use in the processing system 100 are disclosed in commonlyowned U.S. application Ser. No. 12/247,135 filed on Oct. 7, 2008 byKurita et al. and U.S. Pat. No. 6,847,730 issued on Jan. 25, 2005 toBeer et al., both of which are incorporated by reference in theirentireties herein to the extent not inconsistent with the presentdisclosure.

In one embodiment, the processing chambers 103-108 are selectivelysealably coupled to a transferring region 110C of the transfer chamber110 by use of slit valves (not shown). Each slit valve is configured toselectively isolate the processing region in one of the processingchambers 103-108 from the transferring region 110C and is disposedadjacent to the interface between the processing chambers 103-108 andthe transfer chamber 110. In one embodiment, the transfer chamber 110 ismaintained at a vacuum condition to eliminate or minimize pressuredifferences between the transfer chamber 110 and the individualprocessing chambers 103-108, which are typically used to process thesubstrates under a vacuum condition. In an alternate embodiment, thetransfer chamber 110 and the individual processing chambers 103-108 areused to process the substrates in a clean and inert atmospheric pressureenvironment.

It should be noted that the number and orientation of processingchambers (e.g., reference numerals 103-108) shown in the attachedfigures is not intended to limit the scope of the invention, since theseconfigurational details can be adjusted without deviating from the basicscope of the invention described herein. For instance, FIGS. 1 and 3show a seven chamber configuration. Other embodiments of the inventionmay include a configuration with fewer or more chambers depending on thespecific processing to be performed on a specific batch size ofsubstrates without deviating from the scope of the present invention.

Generally, the substrate processing system 100 includes a systemcontroller 190 configured to control the automated aspects of thesystem. The system controller 190 facilitates the control and automationof the overall substrate processing system 100 and may include a centralprocessing unit (CPU) (not shown), memory (not shown), and supportcircuits (or I/O) (not shown). The CPU may be one of any form ofcomputer processors that are used in industrial settings for controllingvarious chamber processes and hardware (e.g., conveyors, motors, fluiddelivery hardware, etc.) and monitor the system and chamber processes(e.g., substrate position, process time, detector signal, etc.). Thememory is connected to the CPU, and may be one or more of a readilyavailable memory, such as random access memory (RAM), read only memory(ROM), floppy disk, hard disk, or any other form of digital storage,local or remote. Software instructions and data can be coded and storedwithin the memory for instructing the CPU. The support circuits are alsoconnected to the CPU for supporting the processor in a conventionalmanner. The support circuits may include cache, power supplies, clockcircuits, input/output circuitry, subsystems, and the like. A program(or computer instructions) readable by the system controller 190determines which tasks are performable on a substrate. Preferably, theprogram is software readable by the system controller 190, whichincludes code to generate and store at least substrate positionalinformation, the sequence of movement of the various controlledcomponents, and any combination thereof.

FIG. 1 is schematic plan view of one embodiment of a substrateprocessing system 100 that includes six processing chambers (e.g.,reference numerals 103-108), a load lock chamber 102, and a substratecarrier transfer robot 111 disposed within the transferring region 110Cof the transfer chamber 110. In one configuration, the processingchambers 103-108 are selected from a physical vapor deposition (PVD)chamber, a plasma enhanced chemical vapor deposition (PECVD) chamber, alow pressure chemical vapor deposition (LPCVD) chamber, a hot wirechemical vapor deposition (HWCVD) chamber, a plasma nitridation chamber(DPN), a ion implant/doping chamber, an atomic layer deposition (ALD)chamber, a plasma etching chamber, a laser anneal chamber, a rapidthermal oxidation/nitridation (RTO/N) chamber, a rapid thermal annealing(RTA) chamber, a substrate reorientation chamber (e.g., flippingchamber), a vapor etching chamber, a forming gas or hydrogen annealingchamber, and/or a plasma cleaning chamber. According to one embodimentof the invention, the substrate processing system 100 includes a firstprocess chamber 103 and a second process chamber 108 (e.g., FIGS. 1 and3). In one embodiment, the first process chamber 103 is configured todeposit a specific type of film, and the second process chamber 108 isconfigured to form a different type of film(s) on a substrate surface.For example, the first process chamber 103 can be used to process one ormore silicon-containing films and the second process chamber 108 can beused to process one or more metal-containing films to form a highquality solar cell junction. An example of an exemplary PECVD typeprocessing chamber that may be one or more of the processing chambers103-108 as well as exemplary processes that may be performed areillustrated and subsequently discussed in conjunction with FIG. 9.

FIGS. 1 and 3 illustrate embodiments of the substrate processing system100 that are adapted to transfer and process a plurality of solar cellsubstrates, hereafter substrates “S” arranged in planar arrays, orbatches, within the processing system 100. In one embodiment, eachsubstrate transport interface 150 as well as each transfer chamber 110may include a substrate carrier transfer robot 111 having an endeffector 112 to facilitate transfer of a batch of substrates S throughthe processing system 100 as described herein. In one embodiment, theprocessing system 100 is adapted to transfer and process a batch ofsubstrates S that are positioned in a planar array on a carrier 101 bymoving in both vertical and horizontal directions. In one embodiment,the carrier 101 is adapted to hold and retain the substrates S duringthe various transportation and processing steps performed on thesubstrates S within the processing system 100. In this configurationmultiple substrates S are transferred, supported, and processedsimultaneously to improve the system throughput, reduce the number ofrequired transferring steps, and improve the cost of ownershipassociated with processing and forming a solar cell device.

FIG. 2 illustrates a plan view of one embodiment of the carrier 101 thatis adapted to retain 30 substrates S on the carrier 101. In oneconfiguration, the carrier 101 has a plurality of substrate supportingrecesses 101A formed in the carrier 101 to support and laterally retainthe substrates S during the movement of the carrier 101 through thesubstrate processing system 100. In one embodiment, the carrier 101 isadapted to hold at least about 10 substrates S at a time in a planararray. In one embodiment, the carrier 101 is adapted to hold betweenabout 30 and about 80 substrates S at a time in a planar array. In oneembodiment, the carrier 101 is adapted to hold greater than 80substrates S at a time in a planar array. In one configuration therecesses 101A formed in the surface of the carrier 101 have lateraldimensions that are less than about 1 mm larger than the dimensions ofthe substrate S and have a depth from about 0.1 mm to about 0.3 mm. Forexample, a solar cell substrate S may have dimensions 156 mm×156 mm×0.2mm, and the recesses 101A may have corresponding dimensions 158 mm×158mm×0.3 mm. In another embodiment, the carrier 101 may be a flat carrierwithout recesses. The carrier 101 may include pins or bosses extendingtherefrom to retain the substrates S thereon. In one embodiment, thecarrier 101 is made of a carbon fiber composite material with aprotective coating, such as silicon carbide, formed thereon.

Referring to FIGS. 1 and 3, the processing system 100 may be configuredto receive unprocessed substrates S into the substrate transportinterface 150 from an upstream location (e.g., an upstream processingmodule in a solar cell fabrication line) and transport processedsubstrates S out of the substrate transport interface 150 to adownstream location (e.g., a downstream processing module in a solarcell fabrication line). In general, the substrate transport interface150, depicted in FIGS. 1 and 3, includes a substrate transfer module153, a substrate interface module 155, and a substrate transfer module157.

In operation, an empty substrate carrier 101 is generally loaded withunprocessed substrates S in the substrate transfer module 153. In oneembodiment, the substrates S are transported to the substrate transportinterface 150 via one or more modular conveyors 123.

In the embodiment depicted in FIG. 1, a modular conveyor 123A ispositioned on each side of the substrate transport interface 150 fortransporting unprocessed substrates S to the substrate transfer module153 from an upstream location. Additionally, a modular conveyor 123B ispositioned on each side of the substrate transport interface 150 forreceiving processed substrates S from the substrate transfer module 157for transportation to a downstream location. In the embodiment depictedin FIG. 3, a single modular conveyor 123 is positioned to transportunprocessed substrates S for loading into the substrate transfer module153 and to receive processed substrates S from the unloading module 157for transportation to a downstream location.

The substrates S may be transported on the modular conveyors 123individually or in batches, such as in cassettes or stack boxes. In oneembodiment, the substrates S are removed from the modular conveyor 123or 123A and transferred into a receiving area 124 in preparation forloading the substrates S onto a carrier 101 positioned in the substratetransfer module 153. In one embodiment, the substrate transfer module153 includes one or more substrate transfer robots 122A for transferringthe substrates S from the receiving area 124 into a desired position onthe substrate carrier 101. In one embodiment, the substrate transferrobots 122A may be SCARA, six-axis, parallel, or linear type robots thatcan be adapted to transfer substrates from one position within theprocessing system 100 to another. In one example, the substrate transferrobots 122A are Quattro Parallel Robots that are available from AdeptTechnology, Inc. of Pleasanton, Calif.

In the case of stack boxes or cassettes, once the substrates S areunloaded from the respective stack box or cassette, the empty stack boxor cassette is returned to the modular conveyor 123 or 123A fortransport either back upstream (FIG. 1) or downstream (FIG. 3) forfurther use.

In one embodiment, after filling up the carrier 101 with substrates S,the carrier 101 is transferred into the substrate interface module 155via a substrate carrier transfer robot 109 located in the substrateinterface module 155. In one embodiment, the substrate carrier transferrobot 109 has an end effector 113 configured to retrieve the substratecarrier 101 from the substrate transfer module 153 and transfer thesubstrate carrier 101 into the load lock chamber 102. In one embodiment,the substrate carrier transfer robot 109 is further configured toretrieve the substrate carrier 101 from the load lock chamber 102 andtransfer the substrate carrier into the substrate transfer module 157.In one embodiment the substrate carrier transfer robot 109 is configuredto move the substrate carrier 101 vertically as well as horizontally. Inone embodiment, the substrate carrier transfer robot 109 is similar tothe substrate carrier transfer robot 111. In another embodiment, thesubstrate carrier transfer robot 111 incorporates a conveyor mechanismcoupled to lift and rotate mechanisms.

It should be noted that not all regions of the carrier 101 need to befilled during processing. For example, a substrate S may have beenbroken in an earlier process. In some cases, a partial batch ofsubstrates S may be intentionally processed within the processing system100. In some cases, when a partial batch of substrates S are to beprocessed, it may be desirable to insert one or more dummy substrateswithin a batch of substrates S to minimize the exposure of the chambercomponents (e.g., susceptor) directly to the processing environment.

In one example, the load lock chamber 102 comprises a plurality ofisolatable regions (e.g., substrate sub-chambers 820, 822, 824illustrated in FIG. 8) that allow the unimpeded movement of multiplesubstrate carriers 101 and/or substrates S into and out-of the load lockchamber 102 from the transfer chamber 110 or the substrate interfacemodule 155. An example of an exemplary load lock chamber 102 having aplurality of isolatable regions is illustrated and subsequentlydiscussed in conjunction with FIG. 8.

After receiving the substrate carrier 101 and the substrates S into aregion of the load lock chamber 102, such as sub-chamber 820 (FIG. 8),the sub-chamber 820 is closed and pumped down to a desired pressureusing a vacuum pump (not shown). After achieving a desired pressure inthe sub-chamber 820, the substrate carrier 101 and the substrates S arethen received by the end effector 112 of the substrate carrier transferrobot 111 contained in the transfer chamber 110. The substrate carriertransfer robot 111 may then transfer the substrate carrier 101 and thesubstrates S into one of the processing chambers, such as processingchamber 103. In one example, a PECVD amorphous silicon depositionprocess is then performed on the substrates S positioned in theprocessing chamber 103.

In one embodiment, the substrates S are crystalline silicon substrateshaving p-type base regions. A mixture of gases includingsilicon-containing compounds, such as silane (SiH₄), disilane (Si₂H₆),tetrafluorosilane (SiF₄), or other silicon-containing compounds usefulfor depositing a layer of amorphous silicon directly onto a surface ofthe crystalline silicon substrates S. An n-type precursor, such asphosphine (PH₃) is delivered to the processing chamber along with thesilicon-containing compounds in order to provide an n-doped amorphoussilicon film layer deposited on the substrates S from the gas mixture.In one embodiment, the doped amorphous silicon film is deposited at afilm thickness from about 100 Å to about 1000 Å.

After performing a desired solar cell formation process on thesubstrates S, the substrate carrier 101 and the substrates S are thentransferred by the substrate carrier transfer robot 111 into anotherprocessing chamber, such as the processing chamber 104. In one example,a passivation layer deposition process is performed on the substrates Spositioned in the processing chamber 104. An example of such apassivation layer process is subsequently described below in the sectionentitled, “Passivation Layer Deposition.”

In one embodiment, the processing system 100 may further include aprocessing chamber for reorienting, or flipping, the substrates S, suchas the processing chamber 105. In such an embodiment, the substrates S,having been processed on one side, may then be transferred into theprocessing chamber 105 for reorienting the substrates S such that theopposite side may be processed. For instance, if an upwardly facing sideof each substrate is first processed, the processing chamber 105reorients each of the substrates S such that the previously upwardlyfacing side faces downwardly and the previously downwardly facing sidefaces upwardly for subsequent processing. After reorienting thesubstrates S, the substrates S may then be transferred into subsequentprocessing chambers, such as processing chambers 106, 107, or 108 forprocessing the opposite side of the substrates S prior to transfer backinto the load lock chamber 102. In one embodiment, the substrates S aretransferred into processing chamber 106, such as a PVD chamber, and ametallization type deposition process is performed on the substrates S.Thus, processing of a first side of the substrates S, flipping of thesubstrates S, and processing of the opposite side of the substrates Smay all be achieved within the processing system 100 without breakingvacuum within the system. In one embodiment, a metallization typedeposition process is performed on the substrates S

After performing desired solar cell formation processes on thesubstrates S, the substrate carrier 101 and the substrates S are thentransferred by the substrate carrier transfer robot 111 from thetransfer chamber 110 to a region of the load lock chamber 102, such assub-chamber 822 (FIG. 8). After achieving a desired pressure in thesub-chamber 822, the substrate carrier 101 and the substrates S are thenretrieved from the load lock chamber 102 by the substrate carriertransfer robot 109 within the substrate interface module 155. Once thesubstrates S are transferred back into the substrate interface module155, the substrate carrier 101 and the substrates S are transported intothe substrate transfer module 157 via substrate carrier transfer robot109 for unloading the individual substrates S from the substratetransfer interface 150. In one embodiment, each of the substrates S arethen transferred from the substrate transfer module 157 to the substrateexit area 126 via one or more substrate transfer robots 122B containedin the substrate transfer module 157. After the substrates S arepositioned in the exit area 126, the empty substrate carrier 101 may bestored, cleaned, and/or transported back into the substrate transfermodule 153.

After positioning the substrates S in the exit area 126, the substratesS are then transferred to the modular conveyor 123 or 123B where theprocessed substrates S are transported to downstream process modules inthe solar cell fabrication facility. This configuration may be used toallow one or both sides of a solar cell substrate to be processed in avacuum or inert environment without exposure to atmosphericcontaminants.

It should be noted that the number of transferring steps and processingsteps discussed herein are not intended to limit the scope of theinvention and can vary in the number of processes performed on the solarcell substrate S, vary in the number of processing chambers that areused to from a solar cell, and vary in the order and sequence ofprocesses without deviating from the basic scope of the inventiondisclosed herein. For example, the processing system 100 may includeonly a single processing chamber 103 rather than the plurality ofprocessing chambers 103-108 coupled to the load lock chamber 102 via thetransfer chamber 110. In such a configuration, the single processingchamber 103 is coupled to the load lock chamber 102 with or without theneed for the transfer chamber 110 and the substrate carrier transferrobot 111. The load lock chamber 102 may include a substrate carriertransport means, such as a conveyor mechanism similar to carrierconveyors subsequently described herein with respect to FIGS. 4A-4C and5.

FIG. 4A is a schematic front view of a substrate transport interface 150according to one embodiment of the present invention. As previouslydescribed, the substrate transport interface 150 generally includes thesubstrate transfer module 153 where substrates S are loaded onto asubstrate carrier 101, the substrate interface module 155 having asubstrate carrier transfer robot 109 that transfers the substratecarriers 101, and the substrate transfer module 157 where substrates Sare unloaded from the substrate carrier 101.

In another embodiment, schematically depicted in FIG. 4B, the functionsof loading substrates S onto and unloading the substrates S off of thesubstrate carrier 101 are both performed in a single substrate transfermodule, such as the transfer module 157. In such an embodiment, thesubstrate transfer module 157 is used both for loading and unloadingsubstrates S onto and off of the substrate carrier 101 using one or moreof the substrate transfer robots 122B. As such, the exit area 126, shownin FIG. 3, is used both as a receiving area and as an exit area aspreviously described. In yet another embodiment, loading and unloadingof substrates S the substrate carrier 101 may be performed while thesubstrate carrier 101 is positioned on the substrate carrier transferrobot 111.

In one embodiment, the substrate transfer module 153 includes a cleaningmodule 151 that receives and cleans a substrate carrier 101. In oneembodiment, the substrate carrier transfer robot 109 located in thesubstrate interface module 155 retrieves an empty substrate carrier 101from the substrate transfer module 157 and transfers the empty substratecarrier 101 into the cleaning module 151. In another embodiment, anempty substrate carrier 101 is transported from the substrate transfermodule 157 into the cleaning module 151 via a modular conveyor 185,which links the substrate transfer module 157 with the substratetransfer module 153 as shown in FIG. 4C. In one example, it is generallydesirable to clean the substrate carriers 101 prior to loadingunprocessed substrates S onto the substrate carriers 101 in order toensure that no debris impedes proper positioning of the substrates Sonthe substrate carriers 101.

FIG. 5 is a schematic, front, cross-sectional view of a cleaning module151 according to one embodiment of the present invention. The cleaningmodule 151 generally includes a carrier conveyor 510, lift mechanisms520, a cleaning mechanism 530, a waste bin 540, and an enclosure 550. Inone embodiment, an empty substrate carrier 101 is received onto thecarrier conveyor 510 from the substrate carrier transfer robot 109 in aninlet direction Ai. The carrier conveyor 510 may include one or morerollers, belts, and actuators controlled by the system controller 190for advancing the substrate carrier 101. In one embodiment, sensors,such as capacitive sensors, detect the presence of the substrate carrier101 on the carrier conveyor 510 and send signals to the systemcontroller 190. The system controller 190, in turn, sends signals toactuate the lift mechanisms 520.

In one embodiment, the lift mechanisms 520 are a plurality of cylinders(e.g., pneumatic cylinders) positioned about the carrier conveyor 510.The lift mechanisms 520 are configured to contact the lower surface ofthe substrate carrier 101 and raise the substrate carrier 101 to acleaning position. Once the substrate carrier 101 is in the cleaningposition as sensed by sensors, such as inductive sensors, the systemcontroller 190 sends signals to the cleaning mechanism 530 to clean thesubstrate carrier 101.

In one embodiment, the cleaning mechanism 530 includes a debris removaldevice 532 attached to a linear actuator 534 (e.g., a rodless pneumaticcylinder). The debris removal device 532 is configured to span the widthof the substrate carrier 101, and the linear actuator 534 is configuredto horizontally move the debris removal device 532 the length of thesubstrate carrier 101. In one embodiment, the debris removal device 532is a compressed air device (e.g., an air knife). In this embodiment,once the substrate carrier 101 is in its raised cleaning position, acurtain of compressed air is blown onto the substrate carrier 101 acrossthe entire width of the substrate carrier 101 via the debris removaldevice 532. In another embodiment, the debris removal device 532 is avacuum device configured to lift and remove debris from the substratecarrier 101. The debris removal device 532 is then moved down the entirelength of the substrate carrier 101 via the linear actuator 534 in orderto remove any debris from the substrate carrier 101. The debris removedfrom the substrate carrier 101 is blown or transported into the wastebin 540 positioned at the end of the carrier conveyor 510 for subsequentremoval. Once the debris removal device 532 has moved along the entirelength of the substrate carrier 101, and the substrate carrier 101 isclean, the linear actuator 534 returns the debris removal device 532 toits starting position. In one embodiment, the lift mechanisms 520 areconfigured to tip the substrate carrier 101 to aid in the debris removalprocess.

In one embodiment, after the substrate carrier 101 has been cleaned bythe cleaning mechanism 530, the substrate carrier 101 is lowered backonto the carrier conveyor 510 via the lift mechanisms 520. The cleansubstrate carrier 101 may then be removed from the cleaning module 151by use of the carrier conveyor 510 in an outlet direction Ao.

In one embodiment, the enclosure 550 is configured to retain debriswithin the cleaning module 151 and direct the debris into the waste bin540 during cleaning of the substrate carrier 101. The enclosure 550 isfurther configured to maintain steady state pressure within the cleaningmodule 151 during the cleaning process. In one embodiment, the enclosure550 is a sheet metal structure that supports and encloses components ofthe cleaning module 151.

Referring to FIG. 4A, the substrate transfer module 153 may furtherinclude a lift module 152 for receiving the clean substrate carrier 101from the cleaning module 151 and raising the substrate carrier 101 forloading with substrates S. In one embodiment, the clean substratecarrier 101 is transported from the carrier conveyor 510 within thecleaning module 151 onto a carrier conveyor 154 within the lift module152 through the use of the respective carrier conveyors 510, 154. In oneembodiment, the carrier conveyor 154 is similar to the carrier conveyor510, which includes one or more rollers, belts, and actuators controlledby the system controller 190 for advancing the substrate carrier 101.

In one embodiment, the lift module 152 further includes a lift, orelevator mechanism 156 for raising and lowering the carrier conveyor154. In one embodiment, the elevator mechanism 156 comprises one or morelinear actuators, such as pneumatic, electric, or hydraulic cylinders ormotors. Generally, the clean substrate carrier 101 is received into thelift module 152 at a lower level (i.e., in-line with the cleaning module151) and is raised to an upper level via the elevator mechanism 156controlled by the system controller 190. Substrates S are loaded ontothe clean substrate carrier 101 at the upper level.

In one embodiment, the clean substrate carrier 101 is then advanced ontoa carrier conveyor 158, which is similar to the carrier conveyor 154 viathe respective carrier conveyors 154, 158 controlled by the systemcontroller 190. In one embodiment, the clean substrate carrier 101 isfully loaded with substrates S while it is situated on the carrierconveyor 154. In one embodiment, the clean substrate carrier 101 isfully loaded with substrates S after it is transferred to the carrierconveyor 158. In one embodiment, the substrate carrier 101 is partiallyloaded while situated on the carrier conveyor 154 and partially loadedwhile situated on the carrier conveyor 154 to increase throughput of theoverall system 100.

After the clean substrate carrier 101 is fully loaded with substrates S,the substrate carrier transfer robot 109 transfers the fully loadedsubstrate carrier 101 into the load lock 102 as previously described.After the substrates S on the substrate carrier 101 have been processed,the substrate carrier transfer robot 109 transfers the substrate carrier101 from the load lock 102 into the unloading module 157.

In one embodiment, the substrate transfer module 157 includes a coolingmodule 159 that receives and cools a substrate carrier 101 havingprocessed substrates S positioned thereon. In this embodiment, thesubstrate carrier transfer robot 109, located in the substrate interfacemodule 155 and controlled by the system controller 190, retrieves thesubstrate carrier 101 loaded with processed substrates S directly fromthe load lock 102 and transfers the fully loaded substrate carrier 101into the cooling module 159. In another embodiment, as shown in FIG. 4C,the substrates S are unloaded from the substrate carrier 101 in thesubstrate transfer module 157 prior to transporting the substratecarrier 101 into the cooling module 159. In this embodiment, thesubstrate carrier transfer robot 109 transfers the substrate carrier 101into the substrate transfer module 157 for substrate removal, and theempty substrate carrier 101 is transferred into the cooling module 159via a modular conveyor in a direction opposite to that subsequentlydescribed. In one example, it is generally desirable to cool thesubstrate carrier 101 with or without the processed substrates S thereonfrom a temperature of at least about 350° C. to a temperature at orbelow about 70° C. to prevent excessive native oxide growth on thesubstrates S, which leads to low efficiency solar cells.

FIG. 6 is a schematic, side, cross-sectional view of a cooling module159 according to one embodiment of the present invention. The coolingmodule 159 generally includes a carrier conveyor 610, carrier liftmechanisms 620, a cooling plate 630, and a cooling plate actuator 640.In one embodiment, a substrate carrier 101 loaded with processedsubstrates S is placed onto the extended carrier lift mechanisms 620 viathe substrate carrier transfer robot 109. In one embodiment, the carrierlift mechanisms 620 are a plurality pneumatically actuated (e.g.,pneumatic cylinders) lift pins 622 positioned about the carrier conveyor610 and configured to receive the substrate carrier 101 in theirextended (i.e., elevated) position. Once the substrate carrier 101 isreceived onto the lift mechanisms 620, the system controller 190 signalsthe lift mechanisms 620 to lower the substrate carrier 101 onto an uppersurface of the cooling plate 630.

In one embodiment, the cooling plate 630 is a plate having a base 632made of a conductive material (e.g., aluminum) with cooling tubing 634(e.g., copper tubing) in conductive contact therewith. In oneembodiment, the base 632 is a single block of conductive material. Inone embodiment, the base 632 is a plurality of blocks 633 of conductivematerial supported on a lower surface by one or more support plates 635attached thereto. In one embodiment, the cooling tubing 634 is routed ina serpentine path and positioned within grooves 631 formed in the base632. In one embodiment, the cooling tubing 634 is configured to flow acooling fluid therethrough for cooling the base 632, and ultimately, thesubstrate carrier 101 and processed substrates S. The cooling fluid maybe chilled water (e.g., about 15° C. to about 20° C.) or other suitablecooling fluid.

In one embodiment, the cooling plate 630 is supported by the coolingplate actuator 640. The cooling plate 630 may receive the carriersupport 101 from the lift mechanisms 620 in an extended or upperposition. The cooling plate actuator 640 may be one or more pneumaticcylinders positioned beneath the cooling plate 630 and controlled by thesystem controller 190 to raise and lower the cooling plate 630.

In one embodiment, the cooling plate 630 has a plurality of ports 636disposed therein, which are fluidly connected to a vacuum pump 637 forpulling the substrate carrier 101 tightly against the cooling plate 630to aid in the cooling process. In another embodiment, the cooling module159 includes a forced air device 638 in lieu of or in addition to thecooling plate 630 to aid in cooling the substrate carrier 101.

Once the carrier support 101 and substrates S thereon have been cooledby the cooling plate 630, the cooling plate actuator 640, controlled bythe system controller 190, lowers the cooling plate 630 to place thesubstrate carrier 101 onto the carrier conveyor 610. The carrierconveyor 610 may include one or more rollers, belts, and actuatorscontrolled by the system controller 190 to advance the substrate carrier101 out of the cooling module 159. It should be understood that thecarrier conveyor 610 is configured to advance the substrate carrier 101into or out of the page as schematically depicted in FIG. 6.

Referring back to FIGS. 4A and 4B, the unloading module 157 may furtherinclude a lift module 162 for receiving the cooled substrate carrier 101and substrates S from the cooling module 159 and raising the substratecarrier 101 for unloading the substrates S. In one embodiment, thecooled substrate carrier 101 is transported from the carrier conveyor610 within the cooling module 159 onto a carrier conveyor 164 within thelift module 162 through the use of the respective carrier conveyors 610,164. In one embodiment, the carrier conveyor 164 is similar to thecarrier conveyor 610, which includes one or more rollers, belts, andactuation devices controlled by the system controller 190.

In one embodiment, the lift module 162 further includes a lift, orelevator mechanism 166 for reading and lowering the carrier conveyor164. In one embodiment, the elevator mechanism 166 comprises one or morelinear actuators, such as pneumatic, electric, or hydraulic cylinders ormotors. Generally, the cooled substrate carrier 101 is received into thelift module 162 at a lower level (i.e., in-line with the cooling module159) and is raised to an upper level via the elevator mechanism 166wherein substrate S are unloaded from the cooled substrate carrier 101.

In one embodiment, the cooled substrate carrier 101 is then advancedonto a carrier conveyor 168, which is similar to the carrier conveyor164 via the respective carrier conveyors 164, 168 controlled by thesystem controller 190. In one embodiment, the cooled substrate carrier101 is fully unloaded while it is situated on the carrier conveyor 164.In one embodiment, the cooled substrate carrier 101 is fully unloadedafter it is transferred to the carrier conveyor 168. In one embodimentthe cooled substrate carrier 101 is partially unloaded while situated onthe carrier conveyor 164 and partially unloaded while situated on thecarrier conveyor 164 to increase throughput of the overall system 100.In one embodiment, shown in FIG. 4B, the empty substrate carrier 101 isthen loaded with substrates S on one or more of the respective carrierconveyors 164, 168 via one or more of the substrate transfer robots123B.

In one embodiment, the substrate transfer module 157 further includes abuffering module 170 to provide spacing for storage and staging of oneor more additional substrate carriers 101. In one example, it may bedesirable to store one or more additional substrate carriers 101 withinthe unloading module 157 in order to provide a ready supply of substratecarriers 101 into the system 100. In another example, it may bedesirable to provide a collection area where one or more substratecarriers 101 may be stored within the system 100 if any of thecomponents of the system 100 go down. Generally, the addition of thebuffering module 170 allows optimized utilization of the system 100during fault induced line stoppages. Incorporation of such a module intothe substrate transfer module 157 maximizes efficiency of the overallsystem 100 while minimizing the overall footprint requirements. In oneembodiment, the buffering module 170 is located above the cooling moduleas shown in FIG. 4.

FIG. 7 is a schematic, front view of the buffer module 170 according toone embodiment of the present invention. In one embodiment, the buffermodule 170 includes a plurality of shelves 710 for storing one or moresubstrate carriers 101, a plurality of lifting pins 720 for raising andlowering one or more of the shelves 710, a base plate 730 for supportingthe plurality of lifting pins 720, and a linear actuator 740 forlaterally moving the base plate 730.

In one embodiment, the plurality of shelves 710 includes one or morestationary base shelves 712 and one or more vertically movable shelves714. In one embodiment, the plurality of shelves includes ten or morevertically movable shelves 714. In one embodiment, one or more spacers716 are positioned between each of the shelves 712, 714 in order toprovide sufficient vertical spacing between the shelves 712, 714 toallow for a substrate carrier 101 to rest on each shelf 712, 714. In oneembodiment, the spacers 716 provide at least about 6 mm of spacingbetween each shelf 712, 714. In another embodiment, instead of spacers716, the shelves 712, 714 are spaced apart by supportive brackets havingstaggered supports extending therefrom to support each of the shelves712, 714. In this embodiment, the shelves 712, 714 may have staggeredcutouts to allow the shelves 712, 714 to be raised above the supportsrespectively positioned thereabove. Each of the shelves 712, 714 mayalso be laterally spaced apart as shown in FIG. 7. In one embodiment,each of the shelves 712, 714 are laterally spaced apart to provide atleast about 20 mm lateral spacing between each shelf 712, 714. In oneembodiment, each of the vertical moveable shelves 714 have one or morestaggered features 718 for supporting contact from the lifting pins 720during lifting operations as subsequently described. In one embodiment,the staggered features 718 are tabs extending outwardly from thevertically moveable shelves 714.

In one embodiment, each of the lifting pins 720 is positioned on thebase plate 730. Each lifting pin 720 may include a pneumatic cylinder722 controlled by the system controller 190 for raising and lowering thelifting pin 720. The base plate 730 is, in turn, coupled to the linearactuator 740. The linear actuator 740 may be servomotor driven andcontrolled by the system controller 190.

In operation, a substrate carrier 101 may be individually loaded ontoeach of the plurality of shelves 710 via the substrate carrier transferrobot 109 controlled by the system controller 190. In one embodiment,the shelves 714, positioned above the shelf 712, 714 on which thesubstrate carrier 101 is to be placed, are collectively raised in orderto provide spacing for the end effector 113 of the robot 109 to positionthe substrate carrier 101 therein.

For instance, in order to load a first substrate carrier 101 onto thestationary base shelf 712, the linear actuator 740 first laterallypositions the base plate 730 such that the lift pins 710 are alignedwith the features 718 of the lowest vertically movable shelf 714. Thelift pins 710 are then actuated to extend contacting the features of thelowest vertically movable shelf 714, and raising the lowest verticallymovable shelf 714 along with each shelf positioned thereabove. As aresult, a spacing (e.g., at least about 110 mm) is provided between thestationary base shelf 712 and the lowest vertically movable shelf 714 toallow for placement of the first substrate carrier 101 onto thestationary base shelf 712 via the substrate carrier transfer robot 109.Next, in order to load a second substrate carrier 101 onto the lowestvertically movable shelf 714, the linear actuator 740 positions the baseplate 730 such that the lift pins 710 are aligned with the features 718of the second lowest vertically movable shelf 714. The lift pins 710 arethen actuated to lift the second lowest vertically movable shelf 714along with each shelf positioned thereabove to provide sufficientspacing between the lowest vertically movable shelf 714 and the secondlowest vertically movable shelf 714 to allow for placement of the secondsubstrate carrier 101 onto the lowest vertically movable shelf 714. Theoperations may be repeated until all of the buffer shelves 710 areloaded with substrate carriers 101. As needed, the substrate carriers101 may be subsequently unloaded by essentially reversing the aboveoperations. As such, the loading and unloading of substrate carriers 101on the buffer shelves 710 are carried out using first-in, last-outlogic.

In another embodiment, the buffer module 170 includes only a pluralityof the stationary shelves 712 spaced apart adequately to receive asubstrate carrier 101 on each shelf. In one embodiment, substratecarriers 101 having processed substrates S thereon may be transferredfrom the load lock chamber 102 into the buffer module 170 for a timedcooling sequence controlled by the system controller 190. Once the timedcooling sequence is completed the substrate carrier 101 is transportedonto the carrier conveyor 168 and/or 164 for unloading of the substratesS. In another embodiment, the substrate carrier 101 is first unloadedand then transferred into the buffer module 170 for a timed coolingsequence controlled by the system controller 190. In one embodiment, thesystem controller 190 is used to track each substrate carrier 101throughout the entire system. In this embodiment, the system controller190 is configured to not only keep track of the processing sequences,but it is also configured to keep track of empty substrate carriers 101disposed in various locations throughout the system. In this embodiment,buffering of substrate carriers 101 during system ramp up or ramp downmay be accomplished by tracking the transfer of empty substrate carriers101 throughout the system rather than storing the empty substratecarriers 101 in the buffer module 170.

Load Lock Chambers

FIG. 8 is a cross-sectional view of one embodiment of the load lockchamber 102. The load lock chamber 102 may include a plurality of singlesubstrate transfer compartments/sub-chambers as shown in FIG. 8, oralternatively one or more transfer compartments/sub-chambers, eachsub-chamber for loading and unloading multiple substrates. Load lockchambers that may be adapted to benefit from the invention are describedin commonly assigned U.S. patent application Ser. No. 09/663,862 filedon Sep. 15, 2000, by Kurita et al.; Ser. No. 09/957,784, entitled“Double Dual Slot Load Lock for Process Equipment”, filed Sep. 21, 2001by Kurita et al. and issued on Mar. 21, 2002 as U.S. Pat. Nos.7,105,463; and 10/832,795, entitled “Load Lock Chamber for Large AreaSubstrate Processing System”, filed Apr. 26, 2004 by Kurita et al. andissued on Apr. 24, 2007 as U.S. Pat. No. 7,207,766, all of which arehereby incorporated by reference in their entireties.

The load lock chamber 102 may include a chamber body 812 with aplurality of vertically-stacked, environmentally-isolated, singlesubstrate sub-chambers 820, 822, 824 separated by a plurality ofvacuum-tight, horizontal interior walls 814. Two of the interior walls814 are shown in FIG. 8. Although three single substrate sub-chambers820, 822, 824 are shown in the embodiment depicted in FIG. 8, it iscontemplated that the chamber body 812 of the load lock chamber 102 ofthe invention may include just one load lock chamber or two or morevertically-stacked substrate load lock sub-chambers. For example, theload lock chamber 102 may include N substrate sub-chambers separated byN-1 horizontal interior walls 814, where N is an integer number.

In the embodiment depicted in FIG. 8, the substrate sub-chambers 820,822, 824 are each configured to accommodate a single batch of substratesS, such as a plurality of substrates S disposed on the substrate carrier101 (FIG. 2), so that the volume of each chamber may be minimized toenhance fast pumping and vent cycles. It is contemplated that load lockchambers or sub-chambers of the invention may be configured toaccommodate even larger batches of substrates.

The chamber body 812 can be fabricated from a rigid material suitablefor use under vacuum conditions, such as stainless steel or aluminum.The horizontal walls 814 of the chamber body 812 may be vacuum sealed tosidewalls of the chamber body 812, thereby isolating the substratesub-chambers 820, 822, 824. For example, the horizontal walls 814assembled into the load lock chamber 102 may be continuously welded tothe chamber body 812 to allow greater access to the entire interior ofthe chamber body 812.

Generally, each of the substrate sub-chambers 820, 822, 824 defined inthe chamber body 812 includes two substrate access ports. For example,in FIG. 8, the first substrate sub-chamber 820 disposed at the bottom ofthe chamber body 812 includes a first substrate access port 830A and asecond substrate access port 832A coupled to the transfer chamber 110(FIG. 1) and the substrate interface module 155, respectively. The twoaccess ports may be positioned, for example, on opposite sides of thechamber sidewalls. The substrate access ports are configured tofacilitate the entry and egress of the substrates from the load lockchamber 102. Similarly, the substrate sub-chamber 822 is configured withaccess ports 830B, 832B and the substrate sub-chamber 824 is similarlyconfigured with access ports 830C, 832C. Each of the substrate accessports 830A, 830B, 830C, 1132A, 832B, 832C is selectively sealed by arespective slit valve 826A, 826B, 826C, 828A, 828B, 828C that is adaptedto selectively isolate the substrate sub-chambers 820, 822, 824 from theenvironments of the transfer chamber 110 and the substrate interfacemodule 155. The slit valves 826A, 826B, 826C, 828A, 828B, 828C arepivotally coupled to the chamber body 812 and may be moved between anopen and closed position using an actuator (not shown).

In one configuration, the carriers 101 are supported above the bottom ofeach of the substrate sub-chambers 820, 822, 824 by a plurality ofsubstrate supports 844, which are configured and spaced at an elevationwith the chamber body 812 or the horizontal walls 814.

Processing Chamber Configuration

FIG. 9 is a schematic cross-section view of one embodiment of aprocessing chamber, such as a PECVD chamber 901 in which one or morefilms can be deposited on each of the substrates S in the batch. In oneconfiguration, the PECVD chamber 901 is adapted to deposit one or morelayers on each of the substrates S that are disposed on a carrier 101,as shown in FIG. 9. One suitable plasma enhanced chemical vapordeposition chamber is available from Applied Materials, Inc., located inSanta Clara, Calif. It is contemplated that other deposition chambers,such as hot wire chemical vapor deposition (HWCVD), low pressurechemical vapor deposition (LPCVD), physical vapor deposition (PVD),evaporation, or other similar devices, including those from othermanufacturers, may be utilized to practice the present invention. In oneembodiment, the chamber 901 generally includes walls 902, a bottom 904,and a showerhead 910, and substrate support 930 which define a processvolume 906. The process volume is accessed through a valve 908 such thatthe batch of substrates S, such as a plurality of substrates S disposedon a substrate carrier 101, may be transferred in and out of the PECVDchamber 901. The substrate support 930 includes a substrate receivingsurface 932 for supporting substrates S and a stem 934 coupled to a liftsystem 936 to raise and lower the substrate support 930. A shadow frame933 may be optionally placed over periphery of the carrier 101 that mayalready have one or more layers formed thereon. Lift pins 938 aremoveably disposed through the substrate support 930 to move the carrier101, or the plurality of substrates S in a carrier-less system, to andfrom the substrate receiving surface 932. The substrate support 930 mayalso include heating and/or cooling elements 939 to maintain thesubstrate support 930 at a desired temperature.

The showerhead 910 is coupled to a backing plate 912 at its periphery bya suspension 914. A gas source 920 is coupled to the backing plate 912to provide gas through the backing plate 912 and through the pluralityof holes 911 in the showerhead 910 to the substrate receiving surface932. A vacuum pump 909 is coupled to the PECVD chamber 901 to controlthe process volume 906 at a desired pressure. An RF power source 922 iscoupled to the backing plate 912 and/or to the showerhead 910 to provideRF power to the showerhead 910 so that an electric field is createdbetween the showerhead 910 and the substrate support 930 so that aplasma may be generated from the gases between the showerhead 910 andthe substrate support 930. Various RF frequencies may be used, such as afrequency between about 0.3 MHz and about 200 MHz. In one embodiment theRF power source is provided at a frequency of 13.56 MHz. Examples ofshowerheads are disclosed in U.S. Pat. No. 6,477,980 issued on Nov. 12,2002 to White et al., U.S. Publication 20050251990 published on Nov. 17,2006 to Choi et al., and U.S. Publication 2006/0060138 published on Mar.23, 2006 to Keller et al, which are all incorporated by reference intheir entirety to the extent not inconsistent with the presentdisclosure.

A remote plasma source 924, such as an inductively coupled remote plasmasource, may also be coupled between the gas source and the backingplate. Between processing batches of substrates, a cleaning gas may beprovided to the remote plasma source 924 so that remote plasma isgenerated and provided to clean chamber components. The cleaning gas maybe further excited by the RF power source 922 provided to theshowerhead. Suitable cleaning gases include but are not limited to NF₃,F₂, and SF₆. Examples of remote plasma sources are disclosed in U.S.Pat. No. 5,788,778 issued Aug. 4, 1998 to Shang et al., which isincorporated by reference to the extent not inconsistent with thepresent disclosure.

Passivation Layer Deposition

The following examples describe passivation layer deposition processesthat may be performed during solar cell formation in one or more of theprocessing chambers (103-108), such as the processing chamberillustrated and described with respect to FIG. 9. In one embodiment, aprocess for depositing a hydrogenated SiN layer on solar cell substratesS may be performed using a hydrogen dilution process as follows.

After the substrates S are positioned in the one of the processingchambers 103-108 in the processing system 100, a process gas mixture isflowed into the chamber. The process gas mixture includes a precursorgas mixture and a hydrogen gas (H₂) diluent. The hydrogen gas diluentmay have a flow rate as high as approximately two times the flow rate ofthe precursor gas mixture. The precursor gas mixture may be acombination of silane (SiH₄) and nitrogen (N₂), silane and ammonia(NH₃), or silane, ammonia, and nitrogen. In one example, flow rates fora process gas mixture containing silane, ammonia, and hydrogen may be3.5 sccm, 50 sccm, and 80 sccm, per liter of chamber volume,respectively. Flow rates for a process gas mixture containing silane,ammonia, nitrogen, and hydrogen may be 5 sccm, 16 sccm, 40 sccm, and 80sccm, per liter of chamber volume, respectively.

Next, plasma is generated in the processing chamber 103-108 to deposit aSiN layer on the substrates S, wherein the SiN layer is suitable for useas a combined ARC and passivation layer for a solar cell. Namely, theSiN layer so deposited has a mass density of between about 2.6 and 2.8g/cm³, a refractive index of between about 2.0 and 2.2, and a hydrogenconcentration of between about 5 atomic percent and 15 atomic percent.In one embodiment, a chamber pressure of 1.5 Torr may be maintained inthe chamber and RF power intensity of 0.54 W/cm² at a frequency of 13.56MHz may be applied to the electrodes of the chamber to generate theplasma. Alternatively, low frequency RF power, e.g., 400 kHz, mayinstead be applied to the electrodes.

In another example, a process for depositing a hydrogenated SiN layer ona solar cell substrate using an ammonia-free precursor gas mixture isprovided. After the substrates S are positioned in the second of thechambers 103-108 in the processing system 100, a process gas mixture isflowed into the chamber. The process gas mixture includes silane (SiH₄)and nitrogen (N₂) as precursor gases, and is free of ammonia (NH₃). Theprocess gas mixture, according to one aspect, may have substantially thesame flow rate of nitrogen and silane as the nitrogen and silane flowrates of a conventional SiN process gas mixture. For example, aconventional SiN process gas mixture, i.e., one commonly used in PECVDchambers for forming a SiN passivation layer may contain 5.5 sccm ofsilane and 40 sccm of nitrogen, per liter of chamber volume. The processgas mixture, according to another aspect, may have a substantiallyhigher nitrogen flow rate relative to the flow rate of silane, whencompared to a corresponding conventional SiN process gas mixture. Hence,another process gas mixture may contain 3.5 sccm of silane and 95 sccmof nitrogen, per liter of chamber volume.

Next, plasma is generated in the processing chamber 103-108 to deposit aSiN layer on the substrates S in a manner substantially the same adescribed above in the previous example. As with the previous example,the SiN layer so deposited is suitable for use as a combined ARC andpassivation layer for a solar cell.

In another example, a process for depositing a SiN dual stack film on asolar cell substrate is provided. After the substrates S have beenpositioned in the processing chamber 103-108, a first process gasmixture is flowed into the chamber. The first process gas mixture may beon of the gas mixtures described above. Next, plasma is generated in theprocessing chamber 103-108 to deposit a SiN interface layer on thesubstrates S substantially the same as described above.

Next, flow of the first process gas mixture is stopped, and a secondprocess gas mixture is flowed into the chamber. The second process gasmixture may be a conventional SiN process gas mixture, i.e., onecommonly used in PECVD systems for forming a SiN passivation layer onlarge area substrates, such as flat panel displays. In one example, thesecond process gas mixture may contain 5.5 sccm of silane (SiH₄), 16sccm of ammonia (NH₃), and 40 sccm of nitrogen (N₂), per liter ofchamber volume. Optionally, plasma may be extinguished in the chamberafter flow of the first process gas mixture is stopped and prior to theintroduction of the second process gas mixture. In this case, the firstprocess gas mixture may be substantially purged from the chamber beforethe second process gas mixture is flowed into the chamber.

Finally, a bulk SiN layer is deposited on the interface layer to form adual stack SiN ARC/passivation layer on the substrates S. In this way,the majority of the SiN passivation layer may be deposited by asubstantially faster process without affecting the quality of solar cellpassivation. If plasma is extinguished in the chamber prior to theintroduction of the second process gas mixture, then plasma isre-ignited to enable deposition of the bulk SiN layer.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A processing system, comprising: one or more process chambers eachhaving a substrate supporting surface configured to receive and processan array of substrates positioned on a substrate carrier; a load lockchamber coupled to the one or more process chambers and having one ormore regions with a substrate supporting surface configured to receiveand support the array of substrates positioned on the substrate carrier;and a substrate carrier interface module positioned adjacent the loadlock chamber, the substrate carrier interface module, comprising: one ormore substrate transfer modules configured to load substrates onto thesubstrate carrier and unload substrates off of the substrate carrier;and a substrate interface module having a transfer robot configured totransfer the array of substrates on the substrate carrier from the oneor more substrate transfer modules to the one or more regions of theload lock chamber and from the one or more regions of the load lockchamber to the one or more substrate transfer modules, wherein the oneor more substrate transfer modules include at least one of a substratecarrier cooling module, a substrate carrier cleaning module, and asubstrate carrier buffer module.
 2. The processing system of claim 1,wherein the one or more substrate transfer modules comprise: a substratecarrier cleaning module; a substrate carrier lift module; a firstsubstrate carrier conveyor; and one or more substrate transfer robots.3. The processing system of claim 2, wherein the substrate carriercleaning module comprises: a carrier conveyor configured to receive asubstrate carrier; one or more lift mechanisms configured to lift thesubstrate carrier from the carrier conveyor; one or more cleaningmechanisms configured to clean the substrate carrier; a waste binpositioned to receive debris removed from the substrate carrier; and anenclosure positioned to prevent debris from exiting the substratecarrier cleaning module.
 4. The processing system of claim 3, whereinthe one or more cleaning mechanisms comprises a compressed air devicemounted to a linear actuator, wherein the compressed air devicesubstantially spans the width of the substrate carrier positioned in thesubstrate carrier cleaning module and the linear actuator moves thecompressed air device substantially along a length of the substratecarrier cleaning module.
 5. The processing system of claim 3, whereinthe one or more cleaning mechanisms comprises a vacuum device mounted toa linear actuator, wherein the vacuum device substantially spans thewidth of the substrate carrier positioned in the substrate carriercleaning module and the linear actuator moves the vacuum devicesubstantially along a length of the substrate carrier cleaning module.6. The processing system of claim 2, wherein the substrate carrier liftmodule comprises a second substrate carrier conveyor attached to anelevator mechanism configured to raise the second substrate carrierconveyor for alignment with the first substrate carrier conveyor andlower the second substrate carrier conveyor for alignment with a carrierconveyor disposed in the substrate carrier cleaning module.
 7. Theprocessing system of claim 1, wherein the one or more substrate transfermodules comprise: a substrate carrier cooling module; a first substratecarrier conveyor; a substrate carrier lift module; and one or moresubstrate transfer robots.
 8. The processing system of claim 7, whereinthe substrate carrier cooling module comprises: one or more carrier liftmechanisms for receiving the substrate carrier; a carrier conveyorconfigured to advance the substrate carrier out of the substrate carriercooling module; and a substrate carrier cooling plate configured to coolthe substrate carrier.
 9. The processing system of claim 8, wherein thesubstrate carrier cooling plate comprises: one or more conductive blockshaving one or more coolant carrying conduits therein, wherein the one ormore conductive blocks have an upper surface configured to receive thesubstrate carrier cooling plate; and one or more carrier cooling platelifting mechanisms configured to raise and lower the one or moreconductive blocks.
 10. The processing system of claim 9, wherein thesubstrate carrier cooling plate includes vacuum ports disposed thereinin fluid communication with a vacuum pump.
 11. The processing system ofclaim 7, wherein the substrate carrier cooling module comprises a forcedair cooling device.
 12. The processing system of claim 7, wherein thesubstrate carrier lift module comprises a second substrate carrierconveyor attached to an elevator mechanism configured to raise thesecond substrate carrier conveyor for alignment with the first substratecarrier conveyor and lower the substrate carrier conveyor for alignmentwith a carrier conveyor disposed in the the substrate carrier coolingmodule
 13. The processing system of claim 7, further comprising asubstrate carrier buffer module, comprising: a plurality of shelves eachconfigured to receive a substrate carrier thereon; a plurality oflifting pins configured to raise and lower one or more of the pluralityof shelves; a base plate positioned to support the plurality of liftingpins; and a linear actuator configured to laterally move the base plate.14. A substrate carrier loading and unloading system, comprising: afirst substrate transfer module configured to load an array ofsubstrates onto a substrate carrier, the first substrate transfer modulecomprising: a substrate carrier cleaning module; a first substratecarrier lift module; a substrate carrier loading conveyor; and one ormore first substrate transfer robots; a second substrate transfer moduleconfigured to unload the array of substrates from the substrate carrier,the second substrate transfer module comprising: a substrate carriercooling module; a second substrate carrier lift module; a substratecarrier unloading conveyor; and one or more second substrate transferrobots; and a substrate interface module having a substrate carriertransfer robot configured to transfer the array of substrates on thesubstrate carrier from the first substrate transfer module into aprocessing system and out of the processing system to the secondsubstrate transfer module, wherein the substrate carrier transfer robotis further configured to transfer the substrate carrier from the secondsubstrate transfer module to the first substrate transfer module. 15.The system of claim 14, wherein the substrate carrier cleaning modulecomprises: a carrier conveyor configured to receive a substrate carrierfrom the substrate carrier transfer robot; one or more lift mechanismsconfigured to lift the substrate carrier from the carrier conveyor; oneor more cleaning mechanisms configured to clean the substrate carrier; awaste bin positioned to receive debris removed from the substratecarrier; and an enclosure positioned to prevent debris from exiting thesubstrate carrier cleaning module.
 16. The system of claim 14, whereinthe substrate carrier cooling module comprises: one or more carrier liftmechanisms for receiving the substrate carrier from the substratecarrier transfer robot; a carrier conveyor configured to advance thesubstrate carrier out of the substrate carrier cooling module; and asubstrate carrier cooling plate configured to cool the substratecarrier.
 17. The system of claim 14, further comprising a substratecarrier buffer module, wherein the substrate carrier buffer module,comprises: a plurality of shelves each configured to receive and store asubstrate carrier thereon; a plurality of lifting pins configured toraise and lower one or more of the plurality of shelves; a base platepositioned to support the plurality of lifting pins; and a linearactuator configured to laterally move the base plate.
 18. A method offorming a solar cell device, comprising: cleaning a substrate carrier ina carrier cleaning module; transferring the substrate carrier from thecarrier cleaning module to a substrate loading position in a firstsubstrate transfer module; positioning an array of substrates on thesubstrate carrier in the first substrate transfer module; transferringthe substrate carrier from the first substrate transfer module to a loadlock chamber using a substrate carrier transfer robot; transferring thesubstrate carrier from the load lock chamber to one or more processchambers and processing the array of substrates on the substratecarrier; transferring the substrate carrier from the one or more processchambers to the load lock chamber; transferring the substrate carrierfrom the load lock chamber to a carrier cooling module using thesubstrate carrier transfer robot and cooling the substrate carrier inthe carrier cooling module; transferring the substrate carrier from thecarrier cooling module to a substrate unloading position in a secondsubstrate transfer module; and removing the array of substrates from thesubstrate carrier in the second substrate transfer module.
 19. Themethod of claim 18, wherein cleaning the substrate carrier comprises:receiving the substrate carrier onto a carrier conveyor within thecarrier cleaning module; raising the substrate carrier to a cleaningposition using a plurality of lift mechanisms; cleaning the substratecarrier using a debris removal device coupled to a linear actuator;lowering the substrate carrier onto the carrier conveyor using theplurality of lift mechanisms; and transferring the substrate carrier outof the carrier cleaning module using the carrier conveyor.
 20. Themethod of claim 18, wherein cooling the substrate carrier comprises:receiving the substrate carrier onto a plurality of lift mechanismswithin the carrier cooling module; positioning the substrate carrieronto a cooling plate using the plurality of lift mechanisms; cooling thesubstrate carrier using the cooling plate; lowering the cooling plate toposition the substrate carrier onto a carrier conveyor; and transferringthe substrate carrier out of the carrier cooling module using thecarrier conveyor.